With the booming development of the World Interoperability for Microwave Access (Wimax), in order to maintain its strong competence in the mobile communication field, the 3rd Generation (3G) mobile communication system has to improve its the network performance and reduce the cost of network construction and operation.
Therefore, the standardization working group of the 3rd Generation Partnership Project (3GPP) is now dedicating on researching the evolution of the Packet Switch Core network (PS Core) and the Universal Mobile Telecommunication System Radio Access Network (UTRAN). The research topic is called as System Architecture Evolution (SAE) and Long Term Evolution (LTE) of the access network, wherein the evolved access network is called as the Evolved UTRAN (E-UTRAN).
The evolution of the network aims at providing a network completely based on IP with low delay, high data rate, high system capacity, high coverage and low cost. The evolved mobile communication system is called as the Evolved Packet System (EPS).
FIG. 1 shows the architecture of the E-UTRAN.
As shown in FIG. 1, the E-UTRAN consists of evolved nodes B (E-UTRAN NodeB, eNB for short), and provides radio resources for user access. The eNBs interact with one another through the interface X2. The eNB is connected to the Evolved Packet Core network (EPC) through the interface S1.
In the mobile communication system, services are provided by bearers. Different services correspond to different bearers, so that different service requirements can be met. In order to meet the requirements of the services, bearers have many attributes, such as speed rate, priority and so on. The bearer in the EPS system is defined as EPS bearer.
In the EPS system, the Aggregate Maximum Bit Rate (AMBR) is the maximum speed rate shared by a plurality of bearers of one user. When the other bearers are not transmitting data, any one of the bearers can use the entire AMBR. The AMBR restricts the total speed rate that can be provided by all the bearers sharing the AMBR. The eNB should distribute bandwidth for the bearers according to the AMBR, and should execute the control of the AMBR after the bearer establishment is completed. Upon establishing an EPS bearer, the core network determines whether the bearer shares an AMBR with other bearers according to the attributes of the bearer. Therefore, the Mobile Management Entity (MME) needs to bring the AMBR information of the UE to the eNB upon establishing the bearer.
For a handover through the MME, when the handover is performed from a source eNB to a target eNB, the target eNB also needs to establish a bearer. However, according to the currently used handover method, the target eNB does not know the AMBR information of the UE, so the target eNB can not establish a bearer correctly.